Project Background: Substance use disorders (SUDs) are among the most common and costly of medical conditions and are associated with significant morbidity and mortality. SUDs have been typically managed with time-limited interventions, but there is growing evidence that for a subset of treated patients substance-use problems are recurrent with severe symptomatology and high healthcare utilization. Although there is agreement that new models are needed for these patients with complex SUDs, little research has evaluated the acceptability or use of such approaches. This pilot study proposes to evaluate patients' acceptance and use of a Collaborative Care Management Model (CCMM). The model is informed from chronic care models, but adapted for patients with complex SUDs and high utilization of resource intensive services. Project Objectives: Specific aims of this project include to 1) estimate rates of registr-based eligible patients and rates of recruitment among those seeking VA services via 4 pathways during initial 6 months of study, 2) describe patients' use of CCMM services and compliance with monthly monitoring during the initial 6 months of enrollment, and 3) identify the barriers and facilitators to patient engagement with CCMM services from patient and provider perspectives and examine patients' satisfaction with services. A secondary aim of the project will evaluate pre-post change on substance use, psychological distress and health-related quality of life outcomes. These data will provide information to refine the model and support larger evaluation trials of the comparative costs and clinical outcomes of CCMM versus SUD specialty-care as-usual. Project Methods: Over 12 months, the proposed study will enroll 20 patients with complex SUDs and high healthcare utilization. CCMM are designed to provide patient centered care while reducing recurrent utilization of resource intensive services, and delivered by an interdisciplinary team that provides access to and coordination of substance use, mental health and basic medical services. Services will be coordinated using planned, on-demand and proactive office- and telephone-based contacts. Process of care measures, clinical outcomes and patience experience and satisfaction with services will be assessed at 3 and 6 months after enrollment in the study. A treatment response measure will be collected monthly. Descriptive analyses will estimate rates of registry-based eligible patients seeking VA services, initial enrollment, and enrolled patients contacted > 6 times during initial 6 months. Barriers and facilitators to engagement in CCMM services, as well as clinical outcomes, patients' use, experience and satisfaction with services will be reported. Anticipated Impacts: New models of care that address the needs of patients with recurrent and complex substance use problems such as comorbid mental health problems and homelessness could improve efficient utilization of their healthcare, housing stability, quality of care and clinical outcomes.